1 files changed, 16 insertions, 0 deletions
diff --git a/challenge-070/lubos-kolouch/php/ch-2.php b/challenge-070/lubos-kolouch/php/ch-2.php
new file mode 100644
index 0000000000..b85f40040b
--- /dev/null
+++ b/challenge-070/lubos-kolouch/php/ch-2.php
@@ -0,0 +1,16 @@
+<?php
+
+$N = 4;
+$grayCode = ['0', '1'];
+
+for ($i = 2; $i <= $N; $i++) {
+    $revGrayCode = array_reverse($grayCode);
+    $grayCode = array_map(function ($x) { return '0' . $x; }, $grayCode);
+    $revGrayCode = array_map(function ($x) { return '1' . $x; }, $revGrayCode);
+    $grayCode = array_merge($grayCode, $revGrayCode);
+}
+
+$grayCode = array_map(function ($x) { return bindec($x); }, $grayCode);
+echo implode(', ', $grayCode), "\n";
+
+?>